In the tire industry, manufacturers of tires and tire components have endless choices when fabricating such items. For example, the selection of ingredients for the commercial formulations of tires and tire components depends upon the balance of properties desired and the end use such as bias or radial, and its intended end use (e.g., aircraft, truck/bus, or automobile).
An equally important consideration in the selection of ingredients can be the ability to efficiently process the individual components into batch rubber mixes, and then the further downstream processing of those uncured rubber mixes. For example dry solids, particularly dust-free particles like fillers, may be easily air-conveyed and automatically weighed into the required amounts for batch production in internal mixers such as Banbury™ mixers. Bulk solids such as baled polymers, may require cutting into smaller more manageable sizes so that required amounts for batch production are exactly added. Liquids have the same problems of conveying, weighing, but also may have the added concerns due to their volatility and ability to flow without spillage. For example, a viscous liquid may require heating in order to promote required flow rates for accurate weighing and adding to the batch internal mixer without the generation of volatile gas emissions.
Moreover, the further downstream processing of these uncured rubber mixes may be highly dependent upon the specific factory equipment used. Thus, properties of the uncured rubber mixes such as Mooney viscosity and Mooney scorch values can be important variables and parameters to manage in helping to optimize manufacturing efficiency, particularly since rubber processing equipment subsequent to mixing such as roll mills, roller dies, calendars, extruders, and the like can differ significantly in production volumes and rates and in operating temperatures throughout factories throughout the world. Thus, a requirement for an ingredient for these mixes is its ability to contribute to the ease of processing of the uncured rubber mixes. In particular, when fabricating that portion of the tire relied upon for air impermeability, such as the tire innerliner, manufacturers have applied a myriad of approaches including the widespread use of “butyl” rubbers or elastomers in various embodiments.
Butyl rubbers, generally, copolymers of isobutylene and isoprene, optionally halogenated, have widespread application due to their ability to impart desirable air impermeability properties for the tire. Halobutyl rubbers (halogenated butyl rubber) are the polymers of choice for air-retention in tire innerliners for passenger, truck/bus, and aircraft applications. See, for example, U.S. Pat. Nos. 5,922,153, 5,491,196, EP 0 102 844 and EP 0 127 998. Bromobutyl rubber, chlorobutyl rubbers, and branched (“star-branched”) halogenated butyl rubbers are isobutylene-based elastomers that can be formulated for these specific applications. EXXPRO™ elastomers (ExxonMobil Chemical Company, Houston, Tex.), generally, halogenated random copolymers of isobutylene and para-methylstyrene, have also been of particular interest due to their improvements over traditional butyl rubbers. See, for example, U.S. Pat. Nos. 6,293,327, 5,386,864, U.S. Patent Application Publication No. 2002/151636, JP 2003170438, and JP 2003192854 (applying various approaches of blends of commercial EXXPRO™ elastomers with other polymers).
Of the myriad of choices an artisan has in processing the aforementioned elastomeric compositions, selection of the processing aid is of growing importance. Processing aids are an important consideration when processing elastomers for tire innerliners because they can affect the permeability of the cured tire, the ability of the components of the shaped but uncured tire to adhere to one another called “green tack,” and/or the downstream processing efficiency of the uncured rubber mixes. By selecting the appropriate processing aid, a manufacturer can effect the conditions by which the elastomers are processed and many of the properties of the end use articles produced by those elastomers. For example, a lower Mooney viscosity uncured rubber mix may allow for an increase in production rates. However, too low of a Mooney viscosity may result in the stretching or tearing of the uncured rubber mix potentially increasing scrap rates. Similarly, an increase in the Mooney scorch of the uncured rubber mix may allow the use of higher operating temperatures of mills, dies, calendars, extruders, and the like.
In the past, industry generally accepted distillate “cuts” from the refining process or processing oils such as aromatic, paraffinic, naphthenic oils, and mixtures thereof to assist in the processing of elastomeric compositions. See, for example, U.S. Pat. Nos. 5,162,409 and 5,631,316. However, use of these ingredients may result in increasing the permeability of the air membrane such as the innerliner. More recently, polybutene processing aids have been of great interest because of their ability to reduce the permeability of the air membrane component while maintaining the other desirable properties of an in-service tire and/or in tire manufacturing. See, for example, U.S. Pat. No. 6,710,116, U.S. Patent Application Publication No. 2005/0027062, WO 2002/32995, WO 2002/32992, WO 2002/32993, WO 2002/48257, and WO 2004/009700. The use of polybutene processing aids represents a radical departure from past endeavors because these processing aids are produced through polymerization processes not distillate “cuts” from the refining process.
Other background references include WO 2004/058874 and JP 2003292705.
However, even more improvements are needed to provide more options and flexibility to the balance of properties that manufacturers must consider when making decisions on how elastomers should be processed in light of the desired properties of the specific end use articles. For example, it is still desirable to further reduce the permeability of the air membrane component of a tire or to maintain the permeability of the air membrane component and/or reduce the processing restrictions of the uncured rubber mixes. The present invention fulfills this need by providing more options in this regard through the use of processing aids including functionalized polymers described herein.